Anode and method of manufacturing the same



May 23, 1939. J. A. ZITZLER ANODE AND METHOD OF MANUFACTURING THE SAME J. A. ZITZLER May 23, 1939.

ANODE AND METHOD OF MANUFACTURING THE SAME Filed July 3, 1934 2 Sheets-Sheet 2 Q (bl!!! .JZ. "7,7510:

duo: mm;

Patented May 23, 1939 UNITED STATES PATENT OFFICE ANODE AND METHOD OF MANUFACTURING THE SAltIE Application July 3, 1934, Serial No. 733,657

13 Claims.

This invention relates to anodes and methods of and apparatus for manufacturing the same.

It has long been customary to employ, in vacuum tubes for radio work and similar electrondischarge or thermionic devicesQanodes of generally hollow cylindrical or box-like form, flattened or oblate in cross-section and adapted to enclose the electron-emitting cathode. It is extremely important that such electrode be dimensioned with great accuracy with respect to their inner or electron-collecting surfaces in particular, and that they shall undergo the minimum amount of distortion under conditions of use.

Prior to the present invention, flattened cylindrical box-like anodes were usually constructed of sheet molybdenum or other suitably refractory metal, in two pieces, bent into the desired shape and held against separation and distortion as well as might be by suitable fastening means. Aside from other objections, such anodes were undesirably expensive. Less commonly, two-piece box-like or hollow cylindrical anodes have been made of carbon, especially artificial graphite, which possesses certain properties rendering it distinctly advantageous as a material for anodes, particularly in power tubes. But the relatively frangible nature of this material, coupled with the necessity for accurate dimensioning of cylindrical anodes as above mentioned, not to mention other exacting requirements that have to be met in producing them commercially, have combined to render their manufacture from carbon or artificial graphite and use in vacuum tubes peculiarly difficult and largely impracticable heretofore. For this reason, carbon anodes of the enclosing or box-like type were not made or used extensively prior to the presentinvention; and those that were available were constructed in two parts or sections with joints between them.

One of the objects of the present invention is to overcome the difiiculties heretofore encoun- 'tered in attempting to utilize carbon (e. g., artificial graphite) in making anodes of the hollow cylindrical or box-like type, and to enable manufacture of carbon anodes of this general type,

but of novel construction. and improved characteristics, in a practical manner which is also relatively simple and cheap. This and other objects and advantages of the invention are achieved through the use of a novel method of machining, carbon that enables attaining a high degree of accuracy in the anode surfaces both internal and external, as well as in their arrangementand relation one to another in the finished V-anodep Moreover the resultant anode is one continuous piece or body of carbon, without any joint whatever, something wholly novel in the art and affording marked advantages, both mechanical and electrical, over the built-up or sectional box-like anodes heretofore known.

Hollow cylindrical anodes of the type with which the present invention is concerned may vary considerably in cross-sectional configuration. That is, although the right cross-section is always in the general form of a flattened or m elongated annulus, the inner and outer figures bounding it may be curved or polygonal, or both curved and polygonal; and they may or may not be alike. It is to be understood, therefore, that the terms cylindrical and box-like, as em- 15 ployed herein, are used in a correspondingly broad or generic sense.

Generally described, the method of the invention comprises first providing a carbon block in the form of a flattened right cylinder whose over- 20 all dimensions are slightly greater than those desired for the finished anode. Most desirably, this block is also contoured to approximate more or less roughly the shape of the finished anode, being substantially symmetrical about its major 25 and minor transverse or right-sectional rectangular axes. Next, the block is accurately machined to provide at least two pairs of truly plane lateral faces, these pairs being normal, respectively, to the transverse rectangular axes 30 of the finished anode; and the distance between the faces of each pair being the exact outside dimension of the finished anode measured along the corresponding transverse axis. The block having been thus provided with rectangularly re- 35 lated pairs of plane parallel faces, it becomes possible to locate and form accurately within the block a transversely elongated cathodeenclosing chamber whose major transverse axis is parallel with that of the finished anode and, where 40 there is to be but one such chamber, coincides therewith. However, owing to the frangibility and relative weakness of the carbon material, and to the fact that the finished chamber walls are commonly quite thin (e. g., on the order of 0.05 5 inch), special precautions have to be taken in order not only to avoid failure of the material while being worked, but also to ensure attainment of the necessary degree of accuracy in dimensioning (e. g., within tolerance limits of plus 50 or minus 0.002 inch in practice). Therefore the block must be tightly and rigidly supported laterally during the chamber-forming operation.

Further features and details of the invention will be apparent from the description now to be 55 given illustrating, by way of specific example, how the method of the invention may be employed in manufacturing one typical practical embodiment of the novel one-piece or integral carbon anode. In this description, reference will be made to the accompanying drawings, in which Fig. 1 is a perspective view of a carbon block from which an anode of the form illustrated in Fig. 12 may be made in accordance with the novel method;

Fig. 2 ilustrates the operation or step of machining one of the lateral faces of the block to establish a truly plane gauging surface;

Fig. 3 illustrates the next step of machining the opposite face of the block parallel with the first;

Figs. 4 and 5 illustrate the next operation of machining another pair of lateral faces parallel to each other and at right angles to the first pair;

Fig. 6 illustrates the steps of machining additional lateral faces of the block into accurate relationship with those already established;

' Fig. 6a shows how modified apparatus may be used in performing the operations illustrated, by Fi 6;

Fig, 7 illustrates the step of roughing out by drill the internal chamber of the anode;

Fig. 8 illustrates the operation of accurately surfacing the inner'walls of said chamber;

' Figs. 9 and 10 illustrate the operations of rounding off the corners between external lateral faces;

Fig. 11 illustrates the steps taken in drilling the holes in the anode body for the supporting wires;

Fig. 12 is a perspective view of the finished anode mounted' on the supporting wires;

Fig. 13 is a detail showing a modified form of thesupporting wires; and

Figs. 14 to 1'? are perspective views of further typical-forms of the novel one-piece carbon anode of the invention, to which the same general method of manufacture is similarly applicable.

In applying the principles of the invention to the manufacture of the specific form of carbon anode. illustrated in Fig. 12, a right cylindrical carbon block of the general shape shown in Fig. 1'is first prepared. It will be seen that this particular block is'in the form of two oblate cylinders 89 and I4--I5 intersecting at right angles,

giving the block a somewhat cruciform crosssection. The portion 8-.9, containing the longer or major cross-sectional axis of the block provides the chambered body of the finished anode (Fig. 12), while the portion l4l5 provides lateral mounting or supporting ribs. To obtain this rough general shape of block shown in Fig. 1, aconvenient length may be extruded from the desired carbon mixcontained in an appropriate carbon press or jumbo having such die shape as to form the exterior surface shown in Fig. 1. As the material is extruded through the die the green carbon rod is cut into short lengths and these rods are baked to the desired temperature in ways well understood in the carbon industry to ensure that the resulting stock rod is either an amorphous carbon or artificial graphite, depending upon the final baking temperature. For most uses'it is desirable to give the extruded rods 2. final bake to such high temperature as to convert the carbon into electrical oiuartificial graphite, although'of course the method is not limited to this.

After therods have been baked to their final desired conditionthey are cut, most desirably, by properly -spaced thin carborundum Iwheels, into blocks having the desired anode length. Fig. 1 shows for illustrative purposes one of these blocks. It is of course an easy matter to make the extruded carbon rods of the desired shape and to cut them into blocks of the desired length, as shown in Fig. 1; but working out the further procedure for producing satisfactory finished anodes has presented a problem of considerable difiiculty, as already stated, due to the accuracy required and to the fragile nature of the carbon material. To produce an accurate anode I have found it desirable to start the shaping operations with the carbon block of Fig. 1 positioned by its original side surfaces l and 2, and a side surface 3 of one of the ribs, as shown in Fig. 2. To accomplish this positioning of the carbon block, an accurately shaped, slidable, metal gauge block 4 for carrying the carbon block, is positioned upon the base 5 of the grinding machine adjacent the grinding wheel 6, and is positioned in respect to the wheel by the adjustable guide stop I secured to the base 5 of the grinding machine. The stop 7 is so adjusted as to permit grinding off an exactly predetermined amount of material from the face 8. As will be noted from Fig. 2, the stop I does not touch the face 9 of the carbon block, but it abuts the slidable gauge block. The operator, aided by the thrust of wheel 6, holds the side of the rib l4 against the cooperating shoulder 3 of the recess or groove in gauge block 4 which receives said rib, while sliding the gauge block 4 in a direction perpendicular to the plane of the paper inFig. 2 and into engagement with the grinding wheel 6, as guided by the contact of the gauge block with the stop 1 whose plane guiding surface is normal to the wheel arbor. As the gauge 4 and carbon block carried thereby are slid in this direction, the grinding wheel makes an accurate plane surface on the carbon block along the lateral face 8. This plane surface is normal to a line 23 that will be the major axis of a right section of the finished electrode; and said plane surface constitutes a true plane of reference for succeeding operations.

For machining the opposite lateral face 9 of the carbon block into a truly plane surface also normal to the major cross-sectional axis, use is made of a second grinding machine combination or unit shown diagrammatically in Fig. 3. The sliding gauge block II in this machine unit is proportioned differently from the gauge block t of the unit shown in Fig. 2; so that in use it exerts upon the carbon block no lateral thrust tending to force the carbon block against the grinding wheel, but onlya vertical thrust against the block surfaces I, 2. The position of the carbon block'in respect to thegrinding wheel l3, upon which depends the amount of material that will be ground off face 9, is determined in this case by the position of the guide stop 52, whose vertical plane grindingsurface, like that of guide stop I, is also normal to the Wheel arbor. Against this plane guiding surface, the reference plane face 8 of the carbon block is caused by the operator to bear firmly and to be guided thereby during the grinding of facet. It is to be noted that in this operation the rib l5 of the carbon block does not contact the shoulders of the recess or groove in gauge block I l which receives said rib loosely.

As the result of this operation, lateral face 9 is rendered accurately plane and parallel to lateral face 8, and therefore also normal to the major axis 23 of anyright section of thecylindrical T Cir carbon block, Moreover, by setting the guide stop I2 at the proper distance from the grinding wheel I3, the true plane faces 9 and 9 are established equidistant from or symmetrical with respect to'line I 5 which, in the finished anode, is the minor axis of any right section through the cylindrical anode. Also, the distance between the plane faces 8 and 9 is the exact over-all dimension of the finished anode along any major sectional axis 23'.

It will be understood, of course, that the right sectional axes or center lines of the initial carbon block (Fig. 1), if the stock from which the block is cut is properly made, approximately coincide with the corresponding axes I5" and 23 of the finished anode, variation from exact coincidence being allowed for by the slight oversizing of the rough block already referred to.

plane surface of frame or base I6 of another grinding machine, as shown in Fig. 4. No sliding gauge block is used in this grinding operation as the carbon block can be accurately slid along on the machined surface of frame I6 with the rib I4 in contact with the vertical plane guiding face of stop IIwhich is normal to the arbor of grinding wheel I8. Either the face 8 or the face 9 may be placed in contact with the surface of frame I6, since both are plane; but since face 8 was the first surface machined and was the gauging surface for the previous operation, face 8 is here employed as the reference plane. This operation grinds off the outer face of rib I5 to an extent determined by the setting of guide stop I1; and the resultant truly plane face is normal to the minor sectional axis I5.

In the next step of the method the carbon block is placed in a similar machine, as shown in Fig. 5, but with the stop I9 properly adjusted to bring the outer face of the opposite rib against the grinding wheel 20 to render that face also truly plane and normal to axis I5, as well as to establish it at the same distance from axis 23 as the outer face of the ground rib: I5. In order to accomplish this result, the carbon block is turned end for end from the position shown in Fig, 4; the face 8 of'the carbon anode again being preferablyemployed as the reference plane and resting upon the plane surface of the base or frame 2I of the grinding machine as the block, also guided by stop I9, is moved lengthwise (i. e. perpendicularly to the plane of the paper) to bring the outer face of rib I4 against the grind ing wheel. I

With the foregoing steps in the method completed, the four extreme outer lateral faces of the cylindrical carbon block have been accurately ground to planes containing elements of the cylinder. The opposite faces of each pair are exactly parallel, and the two pairs .are exactly at right angles to each other, 1

The next step is to render the remaining lateral faces of the cylindrical block truly plane, as well as respectively parallel to and symmetrical about the median planes passing through the cross-sectional axes I5 and 23. In order to accomplish this, the carbon block is placed in the grinding machine of Fig. 6 with one of the plane faces, face 8 for example, resting on the plane surface of grinding base or frame 22. Inthis position the ground plane surface of face 8 establishes the vertical position of the carbon block in respectto the grinding machine; and the plane outer face of rib I4, contacting with the plane vertical guiding face of stop 23 '(normal to the wheel arbor), determines the side position of the carbon block in respect to the grinding wheel 24. That is, the center lines or axes I5 and 23' are positioned by the parallel plane faces 8 and I4, respectively. No gauge block for carrying the carbon block is necessary in this operation, because the carbon block is slid along past the grinding wheel 24 with the plane face 8 directly in contact with the plane upper surface of the machine base 22. This one sliding operation accurately grinds the side face 25'adjacent face 8 parallel to and at the desired distance fromcenter line 23, and the side face 26 of rib I5 parallel to and at the desired distance from center line I5, both faces being rendered truly plane, The grinding wheel 24 has its side and peripheral grinding faces dressed at right angles to each other in this instance, and hence the adjacent finished side or re-entrant faces 25 and 26 are at right angles. Also, the edge of the grinding wheel is rounded as indicated at 24' to provide a fillet at the junction of the finished faces 25, 26.

With the same grinding machine set-up shown in Fig. 6, the remaining three pairs of sides or reentrant faces 21-28, 2930, and 3I-32, of the cylindrical carbon block, can be ground to rectangularly intersecting planes, indicated in dotted lines in Fig. 6, and related to each other and to center-lines or axes I5 and 23' in the same way as are faces 25-46, All that is necessary in order to grind faces 2'I-28, is to turn the carbon block end for end so that the outer face of rib I5 is in contact with the stop 23. Then the carbon block is-positioned in the same machine with the plane face 9 resting on the base 22; whereupon the pairs 29-39, and 3I32 may be ground in the same way as described for pairs 2526 and 21-28.

The operations just described as being performed with the apparatus shown in Fig.6 may,

if desired, be performed with the modified apparatus shown in Fig. 6a. Inthis arrangement the stop 33, replacing stop 23, of Fig. 6, is positioned above the grinding wheel to guide the accurately plane outer face (of rib I5, for example) of the carbon block as it is moved at right angles to the wheel arbor in this grinding operation.

The carbon block has now been accurately machined into the form of a true right cylinder which is of generally flattened polygonal crosssection and whose over-all dimensions along the major and minor axes of any right section are the corresponding dimensions 'of the finished anode. It is important for the purposes of this invention in its best embodiment that the op-.

erations necessary to achieve this condition of the carbon block be performed prior to the operation, presently to be described, of forming the cathode-receiving chamber or chambers therein,

since otherwise it is extremely difficult, if not impossible,to achieve the accuracy of dimensioning and 'of symmetry desirable in the finished anode in order to ensure its optimum performance in service. I

In the specific example being described, the anode is to have a single flattened right cylindrical chamber, coaxial with the outer cylindrical surface of the anode and with its major and minor axes or center-lines at any right section substantially coincident with those of the finished anode as a whole, that is, with axes I5 and 23' aforesaid. In forming this chamber, the first step is the drilling or roughing out of the central chamber of the anode, in the manner indicated in Fig.

7 Inthis; figure, 34 is a jig or die blockmachined to snu ly receive and ri idly confine :laterally-the carbon block which has been externally trued by the machiningoperations alreadydescribed. This jig may .be accurately etand held in any desired position on movablecarriage block 35 by means of ;side -stop ,36 and ends-stop .311. This block 3,5 is,agiapted tobe moved along between parallel ways 38, 39,- secured to bed plate 40 of adrill press. ,Any ,suitablemeans may be provided for holding the carriage blockinany adjusted position. For example, ,the block may be provided with a plurality ofinotches ll spaced apart the distance of the roughing holes to be drilled in .the carbon anode, anda springepressed plunger-.42 in the way 39 mayibearranged to :snap

into each of the notches-4| when the block is moved ,along between the ways.

The externally machined carbon block having been placed in the jig or die block, and the jigbeing so positioned on the carriage block 35 that the axis 23 of thecarbon-blocl: is parallel to ways ,3 .,,;3.9, and vertically below the drill .42, the an- .ordie-block ,34. As indicated in Fig-8, the jig with the partially completed anode laterally enclosed therein, after being removed from the drill-press ,(,Fig. 7) is mounted upon the -bed plate LMe-of a suitable milling machine in the position illustrated, in operative relation to the horizontal rotary ;mill ing ,tool :45 extending longitudinally into the chamber. This. rotary milling-toolis mounted upon a carriage (not shown) whose movementis accurately andprecisely adjusted and controlled to give thetool the exact desired cutting pathindicated bythearrows in Fig. 8; such adjustment being effected by reference to the accurately'machined external surfaces of the anode. The axis of rotation of the tool being parallel to the axis of the cylindrical anode, and remaining so throughout its travel in the indicated cutting path, and the carbon anode being rigidly confined laterally, the inner walls of the anode chamber can thus be machined smooth and trueto precise desired dimensions. a

The operations described thus far comprise those essentialin the new method as applied to the manufacture of the particular type of anode selected iorpurposes of illustration. Most, of the remaining operations now to be described, although desirable practically, are not indispensable but-are designed to smooth or round ofi the external contouring of the anode and render the wall thickness: thereof uniform at all points except Wherethe supporting ribs I4, are located. Accordingly the. carbon anode is now removed from the jig and positioned, as shown in ,Fig. 9, on gthe'bed plate 46 of-another grinding-.machine, with one of, its planefaces (e, grace 8) resting .on said bed plate IThe grinding -wheel :41 has an edge 48 concaved'to roundoffthecorners of the ribs 14, IS, on an-a-rc of suitable .radius. ,Thezouter-faceof the rib l4 (e.-g.)wbeing vguidedhy stop 49,-which;,is set at the proper distam i jomth wh el, the a bon block i push d against the wheel in;a direction at right angles .to-thewheel arbor, whereby one corner of rib l5 i .a cumte y:r nmde of -v T e ar n block is .then turned .;e n d for end and the operation repeated, whereby the lower corner of rib I4 is similarly roL 1 nd.e.d mi. The carbon anode isnext urned venwdhiama t pl t and the othercqrnerof rib l l is rounded ofi. After this the carbon block is again turned end forend and the remain n corne o b. is u d Ihe, tWQ pairs of;corners bounding faces 8 and 9 of theanodearerounded off in the same manner .by'use of th indin m c s -up shown in .F g.,l.0. The anodeis placed ina guide block 50 rec s d .similarlyto th uid car yi blocks of,-F1igs.- 2 3, to receive loosely the ribs [4, l5 and permit the adjacent plane sides to contact the block .di rectly, with the. face 8' (e. g.) abutting againsttheguide stonil. Astheguide block 50 an the carbon anode block are pushed through thegrindingmachine,the concaved edge 52 of the grinding wheel 53 will ,accurately round 011 the lower corner oithe iace9 on; an are substantially parallellwith ,theadjacent inner wall of the anode hamber. xiIheiremaining corners are rounded on in the...same manner as already, described in connection with Fig. 9.

Sincethis particular form of anode, when in use, is intended to be supported on wires as illustrated in .Fig. 12, thenextand final step in its manufacture consists. in boring. the ribs l4, l5, longitudinally .to receive such Wires. In this operation, special precautionsmust be taken in order .toavoid shattering the thin walls of the anode shell, andto maintain the required accurate symmetrical spacing of the wire-support zholesifromthermajor transverse axis of the cathode-enclosing chamber. .For. this reason, the apparatus .illustratedin Fig. vl1 is especially well suitedifor use in;thisboring operation. Referring to ;Fig.;11, ;.54 is .a supporting core or mandrel .formedtofit snugly and accurately within the anode .chamberat all points except where the -mandrel is .chamferedslightlyfor clearance as indicated; atxil and 54 .The' portion 54, howeven between the chamferedportions fits snugly againsttheroundedinner surfaces of the chamber. The-mandrel is clamped in the split yoke member .155, thetwo parts of .whichare secured in clamping relation by adjustable screws 56, which screwsmay also serve to hold the yoke member 55 :to the channel. base .55, longitudinally slidable -upon;the bed plate 51 of a drilling machine some what similar to a lathe, the drill beingshown at -51. In using this apparatus for the purpose :stated, .the carbon anode is forced on over the clamped supporting mandrel until the anode abuts :and is stopped-by the clamp 55. The sliding caririage or channel member is then. moved on base 5'! .towardthe..drill..(,toward the right in Fig. 11), until the end of the anode rib-(e. g. .14) meets the :rotating drill .which has passed through guide hole ;58-.provided1=in;the upper partof the clamp mem-- :ber... Movement ofthe carriagejEB to the right continues'until1hole1'593has been=drilled part Way :through; the rib longitudinally. Carriage 56 is then; moved to-theleft suificiently far to free the .,drill,;-the'carbon: anodeisremoved from the sup- ;porting. mandrel, turned end for end and replaced fthereomdwhereupon the drilling operation is repeatedtolcomplete the boring of the hole from the :opposite. end of the, rib I4. Inthe same way. a

';'S mi-l ar hole-iiszbolied through the entire length of .ribili. ilrh m siti n of. stop 6| onthedrilling machine determines the length of each of the boring cuts thus made from the opposite ends of each rib to complete the entire bore 60. In practice, each such boring cutmay be equal to or slightly greater than one-half the length of the anode. Ordinarily the resultant holes drilled from the opposite ends of each anode rib do not exactly meet, but this is advantageous rather than otherwise, because, when the supporting wires 64, 65 are inserted into these holes, as illustrated in Fig. 12, they are bent slightly with the result that the anode is more firmly positioned thereon. Where the holes are not thus slightly offset, the supporting wires'may be crimped as shown in Fig. 13 to increase the holding action.

It will be evident from the foregoing that the principles underlying the novel method of manufacturing carbon anode are applicable to forms of anode other than that specifically referred to in the above description. Other forms, typical of many which differ in detail from that shown in Fig. '12 but which are also, broadly, of the hollow,

flattened cylindrical type, are shown in Figs. 14 to 17 inclusive.

The anodes shown in Figs. 14, 16 and 17, like that of Fig. 12, are single-chambered, the single chamber being in each case coaxial with the cylindrical anode considered as a whole. The

anode shown in Fig. 15 has two chambers both: of

' to be engaged by supporting channels, instead of being bored for wire supports as the smaller type anodes of Figs. 12, 14 and 15. Furthermore, instead'of forming the carbon'rod stock or rough shape solid, as illustrated in Fig. 1, it is feasible to extrude orotherwise form the stock hollow in the first place, the more or less roughly formed central chamber thus initially provided in the stock approaching in general form and location that which isroughly drilled out, as indicated in Fig. '7, where the cylindrical stock is initially solid. When hollow stock is used, the stepof rough drilling out the cathode-receiving chamber is therefore not required, it being only necessary to mill the chamber walls, as indicated in Fig. 8, in order to dimension the chamber precisely and to smooth and aline its walls accurately. I

The carbon stock from which any of the illustrated types of integral carbon anodes are manufactured by the present method may, if desired, 'be a simple rectangle in cross-section instead a provide it. with lateral plane surfaces of reference by which the inner chamber or chambers of the anode can then be machined accurately to exact desired dimensions and in proper symmetricalfposition,

-"The novel carbon anodeproduced in accordance with the method of the present invention has certain highly desirable and important characteristics distinguishing it from previously known anodes used in electron discharge devices such as vacuum tubes. The fact that it is composed of one integral piece of carbon, without joints, is advantageous electrically with respect both to facilitating tube manufacture and improving the performance of the tube in subsequent use. Mechanically, increased structural strength and rigidity are attained, while the weight of the anode is kept down to a minimum and economy in material is effected. Furthermore, distortion due to unequal expansion and contraction at different temperatures, commonly characterizing two-piece anodes, including twopiece carbon anodes ofwhich the sections are held together by metallic fastening means such as molybdenum bolts, is eliminated in the new anode. The accurate machining of the inner surface or walls (e. g. 62, Fig. 12) of the anode chamber enables precise symmetrical location and spacing of the cooperating enclosed cathode with respect thereto, and hence the attainment of predetermined exact distribution of electrons discharged from the cooperating cathode. The accurately uniform wall thickness prevailing except where the'lateral supporting projections are located, due to the accurate machining of the outer surfaces as well as the inner surfaces, is important from the standpoint of uniform heat emission and promotes efficiency in performance as well as longer operating life of the anode. The new anode therefore; has highly desirable characteristics of great value and importance, adapting'it especially for use in power tubes.

The application is in part a continuation of a copending application of this applicant, Serial No. 615,112, filed June 3, 1932.

What I claim is:

1. The method of making a one-piece carbon anode having the general form of an oblate hollow cylinder and adapted for use in a vacuum tube to enclose a cooperating cathode, which comprises preliminarily forming a carbon block with over-all dimensions somewhat exceeding those of the finished anode and having the general shape of an oblate right cylinder whose right section is approximately symmetrical about two rectangularly intersecting axes of unequal length corresponding approximately to such right-sectional axes of the finished cylindrical anode, accurately machining a lateral face of said block to providea true plane of reference normal to one of suchright-sectional axes of the finished anode, machining an opposite lateral face of the block, while using the first machined face as a gauging surface, to provide a second plane face accurately parallel to the first and at a distance therefrom equal to the desired over-all dimension of the finished anode along that axis, similarly machining, by reference to one of the true plane faces already formed, a second pair of true plane lateral faces onthe block, normal to the other right-sectional axis aforesaid and spaced apart a distance equal to the desired'over-all dimension of the finished anode along that axis, and, while rigidly backing the machined lateral faces of the block, machining to exact dimensions therein a right cylindrical chamber extending longitudinally through said block and elongated transv-ersely in the direction of the longer of said axes. I

2. The method of making a one-piece carbon anode having the general form of an oblate hollow cylinder and adapted for usein a vacuum tube to enclose a-cooperating cathode, which comprisespreliminarily forming a solid carbon block with over-all dimensions somewhat exceeding those of the finished anode and having the general shape of an oblate right cylinder whose right section is approximately symmetrical about two rectangularly intersecting axes .of unequal length corresponding approximately to the right-sectional axes of the finished cylindrical anode, accurately machining a lateral face of said block to provide a true plane of reference normal to one of the right sectional axes of the finished anode, machining an opposite lateral face of the block, while using the first machined face as a gauging surface; to provide a second plane face accurately parallel to the first and at a'distance therefrom equal to the desired over-all dimension of the finished anode along that axis, similarly machining, by reference to one of the true plane faces already formed, a second pair of true plane lateral faces on the block, normal to the other right-sectional axis aforesaid and spaced apart a distance equal to the desired over-all dimension of the finished anode along that axis, and, whilerigidly backing the machined lateral faces of the block, boring said block longitudi-. nally to rough out a flattened or oblate rightcylindrical cathode-enclosing chamber therein elongated transversely in the direction of the longer of said axes and, while still rigidly back.- ing said lateral faces, machining the roughedout chamber to exact dimensions. I 3. The method of making a one-piece carbon anode having the general form. of an oblate hollow cylinder and adapted for use in a vacuum tube to enclose a cooperating cathode, which comprises preliminarily forming a carbon block with over-all dimensions somewhat exceeding those of the finished anode and having the general shape of an oblate right cylinder whose right section is approximately symmetrical about two rectangularly intersecting axes of unequal length corre-' sponding approximately to the right-sectional axes of the finished cylindricalanode, accurately machining a lateral face of said block to provide a true plane of reference normal to one of the right-sectional axes of the finished anode; machining an opposite lateral face of the block, while using the first machined face'as-a gaugingsurface, to provide a second plane face accurately parallel to the first and at a distance therefrom equal to the desired over-all dimension of the finished anode along that axis, similarly machining, by reference to one of the true plane faces already formed, a second pair of true plane lateral faces on the block, normal to the other right-sectional axis aforesaid and spaced apart a distance equal to the desired over-all dimension of the finished anode along that axis, and, while rigidly backing the machined lateral faces of the block, machining therein toexact dimensions a right cylindrical chamber extending longitudinally through said block and coaxial therewith, said chamber being elongated transversely in the direction of the longer of said axes.

4. The method of making a one-piece carbon anode of the cathode-enclosing type which comprises accurately machiningv a carbon block into the form of an oblate right cylinder havingat least two sets of truly plane and parallel lateral faces, said sets being at right angles to each other, and, while rigidly backing the machined lateral faces of the block, machining to desired dimensions therein an oblate cathode-enclosing chamber having its boundary surfaces accurately parallel with the longitudinal central axis of said cylinder.

5. The method of making a one-piece carbon anode of the cathode-enclosing type which comprises accurately machining a carbon block into the form of an oblate right cylinder having at least two sets of truly plane and parallel lateral faces, said sets being at right angles to each other, and, while rigidly backing the machined lateral faces of the block, machining to desired dimensions therein an oblate cathode-enclosing chamber which is coaxial with said cylinder and whose inner walls are accurately parallel with the longitudinal central axis of said cylinder.

6. The method of making a one-piece carbon anode of the cathode-enclosing type which comprises accurately machining a solid carbon block into the form of an oblate right cylinder having at least two sets of truly plane and parallel lateral faces, said sets being at right angles to each other, and, while rigidly backing the machined lateral faces of the block, boring the cylinder longitudinally to rough out an oblate cathodeenclosing chamber and then machining the inner surfaces of the chamber into accurate parallelism with the longitudinal axis of said cylinder.

'7. The method of making a one-piece carbon anode of the cathode-enclosing type which comprises preliminarily forming a carbon block with over-all outside dimensions somewhat exceeding those of the finished anode and having the general shape of a flattened hollow right cylinder, accurately machining said block externally into a true right cylinder with at least two sets of truly-plane and parallel lateral faces, said sets being at right angles to each other, and, while rigidly backing the machined lateral faces of the block, machining the inner walls of the block to provide a flattened right cylindrical cathode-enclosing chamber whose central longitudinal axis is parallel with that of the machined outer cylindrical surfaces of the block.

8. The method of making a one-piece carbon anode of the cathode-enclosing type which comprises preliminarily forming a carbon block with over-all outside dimensions somewhat exceeding those of the finished anode and having the general shape of a fiatened hollow right cylinder, accurately machining said block' externally into a true right cylinder with at least two sets of truly plane and parallel lateral faces, said sets being at right angles to each other, and, while rigidly backing the machined lateral facesof the block, machining the inner walls of the block to provide a flattened right cylindrical cathode-enclosing chamber which is coaxial with the cylindrical block as a whole.

9. The method of making a one-piece carbon anode of the cathode-enclosing type which comprises preliminarily preparing a hollow oblate cylinder composed of suitably refractory carbon material in a single piece, accurately machining surfaces on one side of the cylinder Wall to render them parallel to the longitudinal axis of the cylinder and locate them at the predetermined desired distance from said axis, and then, While rigidly backing the wall surfaces thus machined, machining surfaces on the other side of the cylinder wall to render them also parallel with said vices, said anode consisting of one integral piece of carbon material in the general shape of an oblate hollow cylinder adapted to enclose a cooperating cathode, said anode having its inner and outer wall surfaces accurately parallel to the longitudinal axis of the anode, said surfaces having the smoothness and other physical charactcristics of machined carbon. 7

1 A carbon anode for use in electron devices, said anode consisting of one integral piece of artificial graphite in the general shape of an oblate hollow cylinder adapted to enclose a cooperating cathode and formed externally with projecting portions adapted to be engaged by supporting means, said anode having its inner and outer wall surfaces accurately parallel to the longitudinal axis of the anode, said surfaces having the smoothness and other physical characteristics of machined artificial graphite.

12. A one-piece integral carbon anode in the form of hollow right cylinder that is oblate in right section to provide a cathode-enclosing chamber similarly oblate, the walls of said chamber being accurately parallel to the longitudinal axis of the anode and being for the most part of substantially uniform small thickness, and the surfaces of said walls having the smoothness and other physical characteristics of machined carbon.

13. The one-piece integral carbon anode defined in claim 12, further characterized by the fact that said uniform small thickness is of the order of 0.05 inch.

JOHN AUGUSTA ZI'IZLER. 

